A dye-sensitized solar cell has been developed by Grätzel of Switzerland and his coworker and is the next-generation solar cell attracting attention since it has advantages such as high photoelectric conversion efficiency and a low production cost.
A dye-sensitized solar cell is generally equipped with a working electrode, a counter electrode, a photosensitizing dye supported on an oxide semiconductor layer of the working electrode, and an electrolyte disposed between the working electrode and the counter electrode.
Further improvement of the photoelectric conversion characteristics is required for such a dye-sensitized solar cell, and thus various investigations have been conducted.
For example, a titanium oxide film electrode film structure of a three-electrode structure is disclosed as a titanium oxide film of a dye-sensitized solar cell in Patent Document 1. In this titanium oxide film electrode film structure of a three-electrode structure, a ground layer in contact with a transparent conductive film on a transparent substrate is constituted by an oxide film consisting of anatase-type crystal granular titanium oxide of fine particles having a diameter of from 5 to 10 nm, an intermediate layer provided on the ground layer is constituted by a porous film containing rutile-type crystal needle-shaped titanium oxide having a diameter of from 30 to 200 nm and a length of from 0.5 to 20 μm and anatase-type crystal granular titanium oxide having a diameter of from 5 to 400 nm, and an uppermost layer provided on the intermediate layer is constituted by a titanium oxide film consisting of anatase-type crystal granular titanium oxide having a diameter of from 20 to 400 nm. It has been designed to achieve high photoelectric conversion efficiency in the dye-sensitized solar cell by using a titanium oxide film having such a structure.